The complete study (145 pages, many figures, partly in color) can be ?subject=Bestellung">ordered at a price of 50 € incl. postage at the IWK.
Studies on Violin Bow Hair
Bow hairs are considered most often when they break. Every string player needs to have his or her bow rehaired from time to time, either because the hairs no longer grip the string, regardless of the amount of rosin applied, or because too many have fallen out. Rehairing raises the question whether stronger hairs should be used, as well as many others: Is lower hair strength equivalent to lesser elasticity? Does thinner hair break more easily than thicker hair? To answer these and other questions, Helga Poecherstorfer made a study on bow hairs, which was supported by the following institutions:
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Institut für Wildtierkunde an der veterinärmedizinischen Universität Wien (Institute for Wild Animal Research at the University for Veterinary Medicine, Vienna) (Dr. Steineck, Frau Gabriel) |
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Institut für angewandte Physik an der Technischen Universität Wien. (Institute of Applied Physics at the Technical University, Vienna) (Dr. Tschegg, Günther Igler) |
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Botanisches Institut der Universität Wien (Botanical Institute at the University of Vienna) (Dr. Heide Halbritter) |
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Dick, Inc. (Heinrich Dick) |
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Thomastik-Infeld, Inc. (Herr Frank, Herr Vogl) |
The Types of Bow Hair Under Study
1) Argentine
2) Chinese
3) Bleached
4) Japanese
5) Canadian
6) Mongolian
7) Russian
8) Black
Eight types of hair were studied, examining cross-section, core, elasticity, and the structure of each hair type's surface. The resulting sound of the eight types was then analyzed by using a bowing machine and computerized sound analysis. The largest variance among the eight types was determined to be in the structure of the hair's surface, elasticity, and cross-section examination...sound and hair core analysis resulted in less differentiation among types.
Cross-sections were taken from three sections of each hair type sample for a better comparison. A differentiating characteristic among types is the form of a cross-section. Japanese and Mongolian hairs form a group of hairs with elliptical section, while the second group, Russian, Canadian, Chinese and bleached hairs, shows a circular form. The exceptions are black hair with a hybrid form, and Argentine, which is in a class by itself.
Mongolian and Chinese hairs have the smallest cross-section, the bleached and Canadian hair have the largest, and the other types are in between.
Cross-section Examination (magnified 250 times)
This characteristic was examined wirhin two parameters. The stretching force is the amount of force possible to stretch the hair without deformation. The original length should be retained after the test. The yield force is the force required to cause the hair to break. The stretching limit force was extreme with Chinese and Canadian hairs. Chinese hairs sustain only 2 N (Newtons) before permanent deformation, while Canadian hairs showed high elasticity by sustaining 4.5 N.
This elasticity is also reflected in the yield strength, where the Chinese had the lowest and the Canadian the highest yield strength.
The values for the elasticity coefficient can be divided into two groups: Argentine, Chinese, bleached, Japanese, Canadian and Russian hairs are more elastic at 32%- to 35%. Black and Mongolian hairs stretched less than 30%.
A relationship between cross-section and elasticity is only observed at the extreme variances. The low stretching force and yield force of the Mongolian and Chinese hairs could be related to their small diameter. The fact that these types have a higher elasticity coefficient is presently unclear.
The thicker bleached hairs have a lower elasticity, which is probably attributable to longitudinal cracks in the surface of almost all bleached hair. The Canadian hairs, having the second largest diameter, showed the highest measured tensile strength.
Through use of the electron microscope, remarkable differences in the surface of the hair types can be observed.
Studies showed that horse hair has little core. The Argentine, bleached, and Mongolian hairs show no evidence of a core structure. Russian hair was the only one to show a core throughout the entire length of the hair. All other types show only partial core residue.
By observing hairs with and without rosin, it is clear that rosin sticks to the platelets on the surface of the hair.
Note: This article and illustrations are taken from the scientific paper ("wissenschaftlichen Hausarbeit") by Helga Poechelstorfer who was advised at IWK. The above results were summarized by Dr. Matthias Bertsch.